Hydropneumatic pumping arrangement

ABSTRACT

A hydropneumatic pumping arrangement comprising at least two double-acting hydropneumatic force multipliers, pneumatic chambers of pneumatic cylinders of the multipliers communicating, through two two-position directional valves with an air source, and the chambers communicating through hydraulic non-return valves, with hydraulic pressure and return lines connected to actuating hydraulic cylinders of the associated processing equipment. The valves are cylindrical slide valves, an inlet passage of one slide valve is in communication with an air source and outlet passages are in parallel communication with the pneumatic chambers and with control chambers of another slide valve, outlet passages thereof being in communication with the control chambers of the one slide valve of the other force multiplier for alternate communication of the pneumatic chambers of both multipliers with the air source in the course of travel of the pistons of the pneumatic cylinders thereof. Non-return hydraulic valves are interconnected in two bridge circuits, and there is a system provided for compensating the working fluid flowing out from the chambers of the actuating hydraulic cylinders, which system has its inlets connected with one of the diagonals of each bridge circuit, preferably also communicating them in parallel with the hydraulic chambers of a respective force multiplier, and the other diagonals of each bridge circuit being preferably in communication with the hydraulic pressure and return lines.

The present invention relates to the field of mechanical engineering andmore particularly to "variable displacement" hydropneumatic pumpingarrangements which have found wide application in many branches ofindustry as pressure sources in hydro-electric power units of processingequipment, wherein a wide range of variations in operating speeds andforces is required in the actuating units, for example, in weldingequipment, metal-cutting machines, and rolling mills.

The present invention may be employed most successfully in processingequipment working under conditions of radiation, explosion hazards, inhot and chemical processes, wherein electric control circuits cannot beused.

There are known hydropneumatic pumping arrangements (cf. U.S. Pat. No.2,858,767;) comprising at least two double-acting hydropneumatic forcemultipliers, the pneumatic chambers of the pneumatic cylinder of eachmultiplier communicating, through two two-position directional valves,with an air source, and the hydraulic chambers of both unitscommunicating, through non-return hydraulic valves, with pressure anddrain hydraulic lines connected to actuating hydraulic cylinders of theassociated processing equipment.

In such hydropneumatic pumping arrangements, one of the two-positiondirectional valves of each hydropneumatic force multiplier is acylindrical slide valve acting as a control slide valve, and the othertwo-position directional valve is flat and is kinematically associatedwith the first one, both slide valves being housed in a common body of adistribution panel.

On delivering pressure into the control chamber of the cylindrical slidevalve, the flat slide valve (due to the kinematic association) isshifted to one of the two extreme positions.

The main disadvantage of the "prior art" hydropneumatic pumpingarrangements is their relatively low reliability which is due to thefollowing reasons.

Without proper sealing, it is difficult to eliminate leakage ofcompressed air at the point of contact of the flat slide valve with thebody of the distribution panel, which also essentially reduces theefficiency of the arrangement.

Besides, since all cylindrical valves are arranged unilaterally, thecompressed air in the distributing channel of each valve considerablyincreases the force of friction of this valve against the body of thedistribution panel, which in some cases may cause jamming of this slidevalve.

Another disadvantage of the known hydropneumatic pumping arrangements isthat the hydraulic pressure pistons of the hydropneumatic forcemultipliers are designed as differential members which does not providefor maximum efficiency of the pumping arrangement either, as the volumeof the working fluid forced into the actuating hydraulic cylinders ofthe associated equipment, when their pistons perform a downward stroke,is larger than that of the fluid moved during an upward stroke,resulting in an increased number of working cycle reversals, therebyreducing the efficiency and service life of the associated productionequipment.

It should also be borne in mind that throttling holes made in the headsof the hydraulic pistons of the hydropneumatic force multipliers,through which the working fluid is forced into the chambers of theactuating hydraulic cylinders, create additional pressure difference inthe hydraulic line when their pistons perform downward strokes and causeheating of the working fluid, which also results in reducing the pumpingarrangement efficiency and, in some cases, in the necessity of using acooling system, i.e. increasing operational expenses.

Besides, in the known arrangements, the filling of the hydraulicchambers of each hydropneumatic force multiplier, when the hydraulicpiston performs an upward stroke, is performed through the non-returnvalve as a result of suction in the hydraulic chamber being emptied.

At definite velocities (large flows of the working fluid), this mayresult in partial filling of the hydraulic chambers of the forcemultipliers and, as a consequence, in pressure drops in the pressureline, which causes interruptions in the operation of the pumpingarrangement.

It is an object of the present invention to eliminate the abovedisadvantages.

The invention is aimed at providing a hydropneumatic pumping arrangementwith a system of pneumatic and hydraulic directional valves thateliminates compressed-air leakage from air passages, ensures quickaction of the pneumatic and hydraulic directional valves in the courseof reversal of the hydropneumatic force multipliers, maximum travel oftheir pistons, forced filling of one of the hydraulic chambers of eachforce multiplier during delivery of the working fluid from anotherhydraulic chamber, and maximum uniform flow of the working fluid towardthe actuating hydraulic cylinders, which ultimately permitssubstantially raising the efficiency of the pumping arrangement,increasing its service life and ensuring reliable operation thereof.

These and other objects are attained in a hydropneumatic pumpingarrangement comprising at least two double-acting hydropneumatic forcemultipliers, pneumatic chambers of pneumatic cylinders of these forcemultipliers communicating, through two two-position directional valves,with an air source, and the hydraulic chambers of both force multiplierscommunicating, through non-return hydraulic valves, with pressure andreturn hydraulic lines connected to actuating hydraulic cylinders of theassociated processing equipment.

According to the invention, both two-position directional valves arecylindrical slide valves, one of them being a distributing one and theinlet passage thereof being in communication with the air source, whilethe outlet passages thereof are in parallel communication with thepneumatic chambers of a respective hydropneumatic force multiplier andwith the control chambers of the second two-position directional valvewhich is a control valve, and the outlet passages thereof are inparallel communication with the control chambers of the firsttwo-position directional valve of the other hydropneumatic forcemultiplier for alternate communication of the pneumatic chambers of bothhydropneumatic force multipliers with the air source in the course oftravel of the pistons of the pneumatic cylinders.

The non-return hydraulic valves are interconnected in two bridgecircuits, and there is a system provided for compensating the workingfluid flowing out from the chambers of the actuating hydrauliccylinders, which system has its inlets connected with one of thediagonals of each bridge circuit, preferably also communicating them inparallel with the hydraulic chambers of a respective hydropneumaticforce multiplier. The other diagonals of each bridge circuit arepreferably in communication with the pressure and return lines.

The substitution of the kinematic connection between the control anddistributing two-position valves for a pneumatic one, as well as theintroduction into the pumping arrangement of bridge circuits, and asystem for compensating the working fluid flowing out from the chambersof the actuating hydraulic cylinders, makes it possible to practicallyeliminate compressed-air leakage from the pneumatic chambers, tosimplify the structure of the distributing slide valves, and toeliminate jamming of the power control slide valves in the process oftheir switching, which enhances the reliability and efficiency of thepumping arrangement.

It is recommended that the arrangement has two two-position three-wayvalves with unilateral pneumatic control, and in the cylinder sleevewalls of each force multiplier there are made two rows of radiallyarranged through openings, the openings of one of these rows being incommunication, through a common passage, with the control chambers ofone of the three-way valves, and the openings of the other row with theinlet passage of this valve. The distance between the rows of openingsalong the generatrices of the sleeves is chosen such as to ensuredephasing of the pistons of both force multipliers in the course ofoperation, the time of their joint travel being minimum.

Since the arrival of a command signal at the inlet of the two-positiondirectional valve through the distributing channel of the two-positionthree-way valve is strictly timed, there is a possibility for thepressure pistons of a respective force multiplier to perform a fullstroke and remain at the end of the stroke for a specified period oftime in the case of optimum dephasing of the pistons, which permitsenhancing the efficiency of the pumping arrangement, reducing the numberof working cycles, and increasing the service life thereof.

The coupling of the pneumatic chambers of the pneumatic cylinders withthe three-way valve and further, through a two-position four-way valve,with the control chamber of the power distributor of the other pneumaticcylinder through a row of radially arranged openings communicatingthrough a common channel, permits enhancing the quick action of thepneumatic control circuit and, consequently, to improve its dynamiccharacteristics. The sizes of the control openings may be chosen suchthat they practically do not affect the service life of the seals in theforce multipliers.

The system of working fluid flow compensation may be made up of fourcontrolled non-return hydraulic valves, the outlet of each valve beingin communication with one of the hydraulic chambers of one of the forcemultipliers, and the control chambers of these controlled hydraulicvalves are in communication with the opposite hydraulic chamber of thesame force multiplier, all controlled hydraulic valves being connectedthrough a common inlet with an outlet of a hydropneumatic accumulatorwhich has its inlet communicating with the air source through apneumatic a safety valve and a pneumatic reducer.

As a result of the working fluid being admitted from the return chamberof an actuating hydraulic cylinder through a respective hydraulicdirectional valve passage into the return line, and further, through thenon-return valve of a respective hydraulic bridge circuit, into arespective force multiplier hydraulic chamber, the compensation for theoutflowing working fluid is effected automatically by a respectivecontrolled non-return valve opened by the control pressure from thehydraulic chamber of the other force multiplier from which the workingfluid is forced into the pressure line.

Thus, two-way communication is ensured between the filled hydraulicchamber of each force multiplier and the hydropneumatic accumulator,wherein some excess pressure from the compressed air line is maintained,owing to which forced filling of the hydraulic chambers of the forcemultipliers takes place. Therewith, when stemless chambers of theactuating hydraulic cylinders are emptied, excessive working fluid isalso forced through the return line into the accumulator.

Consequently, the proposed compensation system ensures forced filling ofthe force multiplier chambers in the process of forcing the workingfluid from the other multiplier chamber, which also improves thereliability of the pumping arrangement and rules out the possibility ofpressure drops in the pressure line.

According to one of the exemplary embodiments of the invention, thehydropneumatic pumping arrangement comprises a hydraulic forcemultiplier whose high-pressure chamber is in parallel communication withthe hydraulic directional valves of the actuating hydraulic cylinders,while stem-fitted and stemless chambers of this hydraulic forcemultiplier are in communication with the outlets of the two-positionfour-way hydraulic directional valve, the inlet passages thereof beingin communication with the working-fluid automatic pressure controlcircuit in the course of operation.

This embodiment also enables increasing the efficiency of the pumpingarrangement when it is used in welding, pressing, machine-toolmanufacturing and other equipment, i.e. performing working cycles thatnecessitate rapid feed of the actuating mechanisms to the workpiece withfurther boosting of the force of the actuating hydraulic cylinder, forexample, in multiple clamping devices and welding guns.

This is attained in that the driving mechanism is provided with anautomatic control circuit for the pressure if it exceeds that in thepressure line of the hydropneumatic pumping arrangement.

It is also recommended that the working-fluid automatic pressure controlcircuit has an "n-way" electrically controlled hydraulic directionalvalve whose inlet and return passages communicate with the pressure andreturn hydraulic lines, while the outlet passages with hydraulicpressure regulators communicate, in turn, with the inlet passages of thenon-return valves, and their common outlet communicates with the inletof the two-position four-way electrically controlled hydraulicdirectional valve.

Such an embodiment permits improving the power characteristics of thehydropneumatic pumping arrangement owing to the hydropneumatic forcemultipliers forcing the working fluid into the pressure line with thepressure required for performing auxiliary strokes of the actuatinghydraulic cylinders, the high pressure being built up by the circuit inthe course of boosting the force of the actuating hydraulic cylinders.

According to another embodiment of the invention, the hydropneumaticpumping arrangement comprises a hydraulic force multiplier whosehigh-pressure chamber communicates with the stemless chambers of theactuating hydraulic cylinders and is isolated from the outlet channel ofa hydraulic directional valve by a controlled non-return valve, theinlet channel thereof communicating with the inlet channel of thehydraulic directional valve, and the inlet channel of the valve is inparallel communication with the pressure chambers of actuating hydrauliccylinders and with the "high pressure" chamber of the hydraulic forcemultiplier, the control channel of the non-return valve being incommunication with the other outlet of the hydraulic directional valve.

Such an embodiment permits increasing the pumping arrangement efficiencyand cutting down its manufacturing cost in those cases where theactuating hydraulic cylinders have to be maintained under high pressurefor long periods of time.

This is due to the fact that the leaky hydraulic equipment is removedfrom the high-pressure circuit into the low pressure hydraulic line,since the high-pressure hydraulic chamber of the hydraulic forcemultiplier is connected directly with the stemless chamber of theactuating hydraulic cylinder, and its isolation from the pressurehydraulic line is effected by the controlled non-return valve.

Consequently, the cost of some hydraulic elements is reduced since highpressure in the hydraulic system imposes more stringent requirements onthe structure and performance of the hydraulic equipment.

Given below is a detailed description of specific exemplary embodimentsof the present invention with reference to the accompanying drawings, inwhich:

FIG. 1 shows schematically a hydropneumatic pumping arrangementaccording to the invention;

FIG. 2 shows the pumping arrangement of FIG. 1 associated withprocessing equipment having clamping devices; and

FIG. 3 shows another embodiment of an automatic fluid-pressure controlcircuit.

The hydropneumatic pumping arrangement comprises two double-actinghydropneumatic force multipliers 1 and 2 (FIG. 1), each having apneumatic cylinder with two pneumatic chambers 1a, 1b and 2a, 2b,respectively, and two hydraulic chambers 1c, 1d and 2c, 2d communicatingtherewith.

The pneumatic chambers 1a, 1b (2a, 2b) of each hydropneumatic forcemultiplier, respectively, 1 and 2 communicate with an air source throughtwo two-position directional valves 4 and 5 (6 and 7), and the hydraulicchambers 1c, 1d (2c, 2d) communicate through non-return valves 8a, 8b,8c and 8d (9a, 9b, 9c and 9d) with pressure and return hydraulic linesto which the actuating hydraulic cylinders of the associated processingequipment are connected through a hydraulic directional valve 10.

According to the invention, each two-position directional valve 4 and 5(6 and 7) is a cylindrical slide valve with two control chambers 4a and4b; 5a and 5b; 6a and 6b; 7a and 7b, respectively.

The first two-position directional valve 4 (6) of each said pair (4, 5)and (6, 7) of the two-positional valves is a distributing valve and hasits inlet passage 4c (6c) communicating through a reducer 12 with theair source 3, and outlet passages 4d and 4e (6d and 6e) are in parallelcommunication with the pneumatic chambers 1a, 1b (2a, 2b), respectively,of the pneumatic cylinders of the force multipliers 1 and 2 as well aswith the control chambers 5a and 5b (7a and 7b) of the secondtwo-position directional valve 5 (7) of the same pair 4, 5 (6, 7) oftwo-position valves.

Each two-position valve 5 (7) is a control valve and outlet passages 5dand 5e (7d and 7e) thereof are in parallel communication with thecontrol chambers 6a and 6b (4b and 4a) of the first valve of said secondpair (4, 5) and (6, 7) of two-position valves for alternatecommunication of the pneumatic chambers 1a, 1b (2a, 2b) of the pneumaticcylinders of the hydropneumatic force multipliers 1 and 2 with the airsource 3 in the course of travel of the pistons 1e and 2e.

According to the invention, the non-return hydraulic valves 8a, 8b, 8c,8d and 9a, 9b, 9c, 9d are interconnected in fours, forming two bridgecircuits. One of the diagonals "e-k" (e'-k') of each of these bridgecircuits communicates with the hydraulic chambers 1c and 1d (2c and 2d)of respective hydropneumatic force multipliers 1 and 2, and the seconddiagonals "l-m" (l'-m') of these bridge circuits communicate with thepressure and return hydraulic lines connected to the actuating hydrauliccylinders 11 of the associated processing equipment.

In the apparatus, there is provided a system compensating for theworking fluid flowing out from the chambers 11a and 11b of the actuatinghydraulic cylinders 11 of the associated processing equipment, theinlets of the system communicating with the first diagonal "e-k" (e'-k')of each bridge circuit of the non-return valves 8a-8d and 9a-9d.

According to the invention, the pumping arrangement is also providedwith two-position three-way valves 13 and 14 with unilateral pneumaticcontrol, and in the walls of the sleeve of the pneumatic cylinder ofeach hydropneumatic force multiplier 1 and 2 there are made two rows ofradially arranged through openings 1k and 1m (2k and 2m). The openings1k (2k) of one of these rows communicate through a common passage with acontrol chamber 13a (14a) of one of said three-way valves 13 (14), andthe openings 1m (2m) of the other row with inlet passages 13c and 13d(14c, 14d) of this valve 13 (14). The distance between the rows of theradial openings 1k and 1m (2k and 2m) along the generatrix of the sleeveof a respective pneumatic cylinder is chosen such as to ensure dephasingof the pistons 1e (2e) of both force multipliers 1 and 2 in the courseof their operation within a minimum time period of joint travel of thepistons 1e (2e).

The system of working fluid flow compensation is made up of fourcontrolled now-return hydraulic valves 15, 16, 17 and 18, the outlet ofeach valve communicating with one of the hydraulic chambers 1d, 1c, 2cand 2d, respectively, of one of the force multipliers 1 and 2. Controland control chambers 15a, 16a, 17a and 18a of these valves 15, 16, 17and 18 are in communication with the opposite hydraulic chambers 1c, 1d,2d, 2c, respectively, of the force multipliers 1 and 2.

All the controlled hydraulic valves 15, 16, 17, 18 communicate through acommon inlet 19 with the outlet of a hydropneumatic accumulator 20, andan inlet 21 thereof communicates through a pneumatic safety valve 22 andthe reducer 12 with the air source 3.

In a second embodiment (FIG. 2) of the hydropneumatic pumpingarrangement associated with processing equipment with clamping orrestricting devices A there is provided a hydraulic force multiplier 23(FIG. 2) with its high-pressure chamber 23a being in parallelcommunication with electrically controlled hydraulic directional valves24 having controlling actuating hydraulic cylinders 25, while astem-fitted chamber 23b and a stemless chamber 23c of this forcemultiplier 23 are in communication with outlet passages 26b and 26a of atwo-position four-way hydraulic directional valve 26 whose inletpassages 26c and 26d communicate with a circuit 27 for automatic controlof the working fluid pressure during operation of the pumpingarrangement.

The circuit 27 has an "n-way" electrically controlled hydraulicdirectional valve 28 whose inlet 28a and return passage 28b communicatewith a pressure line 29 and a return line 30, and outlets 28c and 28d,with hydraulic pressure regulators 31 and 32 which, in turn, communicatewith the inlets of non-return valves 33 and 34, respectively, and thecommon outlet thereof communicates with the inlet 26d of thetwo-position four-way hydraulic valve 26.

In a third embodiment of the pumping arrangement, a high-pressurechamber 35a (FIG. 3) of a hydraulic force multiplier 35 is incommunication with stemless chambers 36c of actuating hydrauliccylinders 36 and is isolated from a channel 37a of a hydraulicdirectional valve 37 by means of a controlled non-return valve 38 whoseinlet 38a communicates with an inlet 37b of said hydraulic valve 37. Anoutlet passage 38b of this valve 38 is in parallel communication withpressure chambers 36c of the actuating hydraulic cylinders 36 and withthe high-pressure chamber 35a of the hydraulic force multiplier 35.

In this case, a control channel 39 of the non-return valve 38 is incommunication with another outlet 37d of the hydraulic valve 37.

The principle of operation of the hydropneumatic pumping arrangement isas follows. When pressure is applied from the pneumatic line 3 (FIG. 1)to the pneumatic reducers 12, compressed air is admitted to the firsttwo-position directional valves 4 and 6 of each pair 4 and 5 (6 and 7)of valves. The pressure is applied to the outlet passages 4e and 6e ofthese valves 4 and 6, then to the right-hand pneumatic chambers 1b and2b of the pneumatic cylinders of both hydropneumatic force multipliers 1and 2 which at this moment are at rest, against the left-hand stop.

From the chamber 1b of the force multiplier 1, through two rows ofopenings 1k and 1m in the sleeve of its pneumatic cylinder, pneumaticsignals are applied, respectively, to the control chamber 13a and inletpassage 13c of the two-position three-way valve 13. As a result, thevalve 13 is switched into a position whereat the pneumatic controlsignal from the row of through openings 1m in the sleeve of thepneumatic cylinder of the force multiplier 1 is fed to the outletpassage 13c of the valve 13 and on to the inlet passage 5c of the secondtwo-position directional valve 5 of the first pair of valves 4 and 5.

Control pressure from the outlet passage 4e of the first valve 4 isapplied to the control chamber 5b of the second valve 5 of the same pairof valves 4 and 5 and shifts it to the right (FIG. 1) position whereatthe pneumatic signal from the inlet passage 5c of the second valve 5 isfed to the outlet passage 5e thereof and on to the control chamber 6b ofthe first valve 6 of the second pair of valves 6 and 7.

Simultaneously, a pneumatic signals from the right pneumatic chamber 2bof the pneumatic cylinder of the force multiplier unit 2, via two rowsof through openings 2k and 2m in the sleeve of its pneumatic cylinder,are fed to the control chamber 14a and inlet passage 14c of thetwo-position three-way valve 14.

As a result, the valve 14 is switched into a position whereat thepneumatic control signal from the row of through openings 2m in thesleeve of the pneumatic cylinder of the force multiplier 2 enters theoutlet passage 14c of the valve 14, then proceeds to the outlet passage7e of the second valve 7 of the second pair of valves 6 and 7.

The control pressure from the outlet channel 6e hydraulic of the firsttwo-position valve 6 is applied to the control chamber 7b of the secondvalve 7 of the second pair of valves 6 and 7, shifting it to theright-hand position whereat the pneumatic signal from the inlet passageof the valve 7c is fed to the outlet passage 7e and on to the controlchamber 4a of the first valve 4 of the first pair of valves 4 and 5.

As a result, the valve 4 is switched into the left-hand position (fromthat shown in FIG. 1) whereat pressure is applied to the outlet 4d andon to the left pneumatic chamber 1a of the pneumatic cylinder of theforce multiplier 1, and the right pneumatic chamber 1b thereof is incommunication with the atmosphere.

Consequently, the piston 1e of the force multiplier 1 starts moving tothe right, forcing the fluid from the hydraulic chamber 1d into thehydraulic system. As a result of this movement, compressed-air controlpressure from the outlet passage 4d of the valve 4 is applied to thecontrol chamber 5a of the second valve 5, switching it to the left-handposition.

Simultaneously, the pneumatic signals fed from the pneumatic chamber 1bof the force multiplier 1 through the openings 1k and 1m to the valve 13are removed since the right chamber 1b of the force multiplier 1 is atthat moment in communication with the atmosphere whereby the valve 13 isswitched into the initial right-hand position (FIG. 1).

As the piston 1e of the force multiplier 1 moves to the right, it blocksthe row of openings 1k, and the pneumatic signal is fed to a controlchamber 13a of the valve 13, switching it into the left position.

As the piston 1e of the force multiplier 1 continues moving to the rightit passes by the row of openings 1m, and a control pneumatic signal isfed to the inlet channel 13c of the valve 13, which then proceeds to theinput 5c of the valve 5, to its outlet passage 5d, and on to the controlchamber 6a of the pneumatic valve 6 of the force multiplier 2.

As a result the valve 6 is switched into the left position and theworking pressure is supplied to the outlet passage 6d, then to the leftpneumatic chamber 2a of the pneumatic cylinder of the force multiplier2. The right pneumatic chamber 2b of the pneumatic cylinder of the forcemultiplier 2 communicates with the atmosphere through the outletpassage. The piston communicates with the atmosphere. The piston 2e ofthe force multiplier 2 starts moving to the right, forcing the workingfluid from its hydraulic chamber 2d into the hydraulic line of theapparatus.

At the same time, the piston 1e of the force multiplier 1 continuesmoving to the right as far as it will go, whereupon the working fluid isforced only by the multiplier 2. As the pneumatic valve 6 is switchedinto the left position, the control pressure is supplied from the outletpassage 6d into the control chamber 7a of the valve 7, shifting it tothe left position.

The right pneumatic chamber of the force multiplier 2 being incommunication with the atmosphere removes the pneumatic signals from thecontrol chamber 14a of the valve 14 through the rows of openings 2k, andfrom the inlet passage 14e of the same valve through the rows ofopenings 2m in the sleeve of the pneumatic cylinder of the forcemultiplier 2, whereby the valve 14 is switched to the initial left-handposition.

As the piston 2e of the force multiplier 2 moves to the right, itsuccessively passes by the openings 2k and 2m, thus causing thepneumatic signal to appear at the outlet 7d of the distributor 7. Thesignal enters the control chamber 4a of the valve 4 and switches it tothe right-hand position, thereby actuating the force multiplier 1 andpreparing the valve 13 for the next working cycle. In this case theworking fluid is forced into the hydraulic line from the hydraulicchamber 1d of the force multiplier 1.

This is how continuous forcing of the working fluid into the hydraulicline and rigid coupling of the beginning and end of a working cycle ofone force multiplier as a function of the other's movement are effected.This allows elimination of cycle disturbances of the system, occuring inknown pumping arrangements, owing to the synchronized reversal of theforce multipliers 1 and 2. The arrangement is switched on and starts itsworking cycle automatically regardless of the initial position of thepistons 1e and 2e of the force multipliers 1 and 2, directional valves4, 5, 6 and 7 and valves 13 and 14.

When the working fluid is forced from the hydraulic chamber 1d of theforce multiplier 1, pressure is supplied to the inlet of the hydraulicnon-return valve 8d, then, successively, from the hydraulic line to theinlet of the valve 10 and on to the pressure chamber 11b of theactuating hydraulic cylinder 11.

The working fluid from the return chamber 11a of the actuating hydrauliccylinder 11 is admitted through a respective passage of the valve 10into the return line and, through the hydraulic non-return valve 8b ofthe bridge circuit into the hydraulic chamber 1d of the hydropneumaticforce multiplier 1.

Owing to the volumetric difference of the stem-fitted chamber 11a andthe stemless chamber 1b of the actuating hydraulic cylinder 11, theamount of working fluid forced out from the hydraulic chamber 1c of theforce multiplier 1 equals that forced into the hydraulic chamber 1d.

When the working fluid is forced from the stem chamber 11a of theactuating hydraulic cylinder 11, its amount entering the hydraulicchamber 1d of the force multiplier 1 is less than that forced out of thehydraulic chamber 1c of the multiplier 1 and vice versa, thecompensation for the outflowing amount of the working fluid beingprovided by the controlled hydraulic non-return valve 15 opened by thecontrol pressure from the hydraulic chamber 1c of the force multiplier 1and ensuring two-way communication between the hydraulic chamber 1d andthe hydropneumatic accumulator 20.

From the accumulator 20 an additional amount of working fluid is fed tothe hydraulic system, for which purpose an excessive amount of pressureis maintained therein that is controlled by adjustment of the hydraulicreducer 12 and the pneumatic safety valve 22.

As the piston 1e of the force multiplier 1 moves to the right, theworking fluid, under pressure from the hydraulic chamber 1d thereof, isdirected to the non-return valves 8d and 8b of the hydraulic bridgecircuit and on, through the diagonal "l-m" thereof, into the pressureline to the actuating hydraulic cylinder 11. From the return line,through the non-return valve 8a of the hydraulic bridge circuit, theliquid is delivered into the hydraulic chamber 1c of the forcemultiplier 1.

Compensation for the volumetric difference between the stem-fitted andstemless chambers 11a, 11b of the actuating hydraulic cylinder 11 isprovided by the controlled hydraulic non-return valve 16 connecting thehydraulic chamber 1c of the force multiplier 1 with the accumulator 20and by the control pressure from the respective chamber 1d of the forcemultiplier 1.

In a similar way, the working cycle in the hydaulic line is performed inthe case of the hydropneumatic force multiplier 2.

A valve 40 (FIG. 1) is provided in the pumping arrangement which enablesrapid removal of air from the hydraulic system when it is being filledwith the working fluid.

Thus, the actuating hydraulic cylinder 11 is actuated by an invariableamount of the working fluid transferred from one hydraulic chamber ofthe force multipliers 1 and 2 into the other and vice versa.

The proposed control circuit of the hydropneumatic pumping arrangementhas a rigid coupling relative to the working fluid flow in the actuatinghydraulic cylinder 11 and the pressure source, which provides foroptimal power consumption by the pressure source with respect to thefluid flow at any moment.

The hydropneumatic pumping arrangement, intended preferably, for usewith processing equipment having multiple clamping devices, operates asfollows. In the initial position, as shown in FIG. 2, the pistons of theactuating hydraulic cylinders 25 are in the extreme left-hand positions,their hydraulic directional valves 24 being in a neutral position, whilethe hydraulic force multiplier 23 and its hydraulic directional valve 26are in the right-hand position. The hydraulic valve 28 may be in anyposition depending on the working cycle and the sequence of theworkpieces being clamped by devices A.

When the left-hand solenoids of the hydraulic valves 24 are energized,the latter are switched to the left position, resulting in the workingfluid pressure from the pressure line of the pumping arrangement beingsupplied into the stemless chambers 25a of the actuating hydrauliccylinders 25, and their pistons shift the clamping device A to theupward position.

When the device A is brought to the clamping position, a final switch(not shown) operates the hydraulic valves 26 and 28 (or only 26, if thevalve 28 is already in one of the extreme positions).

The hydraulic valves 26 and 28 being switched to the left positions,supply pressure into the stemless chamber 23c of the hydraulic forcemultiplier 23, whose stem starts moving to the left directing the fluidfrom the high pressure chamber 23a to the inlet of the hydraulic valves24 and on into the stemless chambers 25a of the hydraulic cylinders 25,under a pressure exceeding that built up by the hydropneumatic pumpingarrangement to the same extent as the cross-sectional area of thelow-pressure chamber of the force multiplier 23, exceeds a respectivearea of the high pressure chamber 23a thereof with regard for throttlingby the regulators 31 and 32 that are adjusted to the working pressure inaccordance with the required clamping force.

The hydraulic valve 28 in the left or right working positions providesfor fluid supply from the pressure hydraulic line of the pumpingarrangement into the low-pressure chamber of the hydraulic forcemultiplier 23 through the regulators 31 and 32 adjusted to differentworking pressures, whereby different clamping forces are automaticallyselected during a working cycle.

Since the hydraulic force multiplier 23 operates practically withoutreciprocation of the pistons of the actuating hydraulic cylinders 25,the fluid flow from the force multiplier 23 is negligible and shouldonly compensate for leakage in the high-pressure circuit that includesonly the hydraulic valves 24. At the same time, the regulators 31 and 32having considerable leakage of the working fluid, are switched from thehigh-pressure circuit of the force multiplier 23 to the low-pressurecircuit of the pumping arrangement, that permits this leakage to beignored when chosing the volume of the high-pressure chamber 23a of theforce multiplier 23, hence, its dimensions.

On completion of a processing cycle under elevated pressure, thehydraulic valves 24 and 26 are switched to the right positions (theright-hand solenoids of the hydraulic valves 24 are energized and thesolenoid of the hydraulic valve 26 is deenergized, which causes thepistons of the hydraulic cylinders 25 to move to the extreme leftpositions, and the piston of the force multiplier 23 to return to theinitial position).

The hydraulic valve 28 may be switched both on completion of aprocessing cycle and during it, changing thereby the clamping forceduring the working cycle (if it is required by the process).

In the third embodiment of the pumping arrangement, leaky units areexcluded from the high-pressure circuit of the hydraulic forcemultiplier 35. The high-pressure chamber 35a of this multiplier 35 isdirectly connected with the stemless chamber 36c of the actuatinghydraulic cylinder 36 and isolated from the pressure line of the pumpingarrangement by means of the controlled non-return valve 38.

The third embodiment is recommended for cases where the productionprocess necessitates maintaining the high pressure in the equipment fora long time.

What is claimed is:
 1. A hydropneumatic pumping arrangement comprising:at least two double-acting hydropneumatic force multipliers havingrespective pistons; each having a pneumatic cylinder with two pneumaticchambers and two hydraulic chambers; two pairs of two-positiondirectional valves in the form of cylindrical slide valves with twocontrol chambers, an inlet passage of one directional valve in each pairof valves being in communication with an air source, and outlet passagesthereof being in parallel communication with said pneumatic chambers ofone force multiplier and with said control chambers of the otherdirectional valve of the same pair of valves; outlet passages thereofbeing in parallel communication with said control chambers of said onedirectional valve of the other pair of valves for alternativecommunication of said pneumatic chambers with said air source in thecourse of travel of said pistons; interconnected hydraulic non-returnvalves forming two bridge circuits, one diagonal of each circuit beingin communication with said hydraulic chambers of one force multiplier;hydraulic pressure and return lines communicating with the otherdiagonal of each circuit, for connection thereto of actuating hydrauliccylinders of the associated processing equipment; and a system forcompensating working fluid flowing out of said chambers at saidactuating cylinders, inlets of said system being in communication withsaid one diagonal of each bridge circuit.
 2. The pumping arrangement asdefined in claim 1, further comprising two two-position three-way valveswith unilateral pneumatic control and two rows of radially arrangedthrough openings made in walls of pneumatic cylinder sleeves of saidforce multipliers; openings of one of these rows being in communication,through a common passage, with a control chamber of one of saidtwo-position valves, and openings of the other row communicating with aninlet passage of said two-position valves; the distance between saidrows along the generatrices of said cylinder sleeves being selected suchas to ensure dephasing of said pistons of both force multipliers in thecourse of their operation, the time of one of the pistons holdingagainst the stop position being minimum.
 3. The pumping arrangement asdefined in claim 1, wherein said compensating system is made up of fourcontrolled hydraulic non-return valves, outlets of these valves being incommunication with one of said hydraulic chambers of one forcemultiplier, and said control chambers of the controlled non-returnvalves being in communication with the opposite hydraulic chamber of thesame force multiplier, all controlled non-return valves being incommunication, through a common inlet, with an outlet of ahydropneumatic accumulator whose inlet, through a pneumatic safety valveand a pneumatic reducer, is in communication with said air source. 4.The pumping arrangement as defined in claim 1, further comprising ahydraulic force multiplier having a high-pressure chamber incommunication with hydraulic directional valves of actuating hydrauliccylinders; a stem-fitted and a stemless chamber of said hydraulic forcemultiplier being in communication with outlets of a two-positionfour-way directional valve, outlet passages thereof being incommunication with an automatic control circuit for the working-fluidpressure in the course of operation.
 5. The pumping arrangement asdefined in claim 4, wherein said control circuit includes an "n-way"electrically controlled hydraulic directional valve whose inlet andreturn passages are in communication with said pressure and return linesand whose outlets communicate with hydraulic pressure regulators which,in turn, are in communication with inlets of non-return valves, andtheir common outlet is in communication with an inlet of saidtwo-position four-way directional valve, the inlets thereof beingconnected to said chambers.
 6. The pumping arrangement as defined inclaim 1, further comprising a hydraulic force multiplier having ahigh-pressure chamber in communication with stem-fitted and stemlesschambers of actuating hydraulic cylinders, isolated from one outletpassage of a hydraulic directional valve, inlet passages of said valvebeing in parallel communication with said chambers of the actuatinghydraulic cylinders and with said high-pressure chamber, a controlpassage of said hydraulic non-return valve being in communication withanother outlet passage of said hydraulic directional valve.